For the next five year period, the NTLF plans to continue to serve as a Resource to the biomedical and biochemical communities, providing unique and extensive facilities for high level tritiations, rigorous radiochemical purification and tritium analyses. The Resource's Technological Research and Development and Collaborative Research during this Grant period will concentrate in the following areas: (i). development of new methods for the synthesis and exchange labelling of tritiated molecules, including studies of the reaction mechanisms and limitations of these procedures; (ii). synthesis of tritium labelled molecules of biological interest, including proteins, peptides, oligonucleotides, drugs, hormones and insecticides; (iii). continued development of analytical techniques for the determination of site and level of tritium labelling; (iv). use of tritiated substrates in the solution of problems in structural biology and general biochemistry, with particular emphasis on the application of tritium NMR techniques to these problems. Some of the projects included in the categories above will be: preparation of high specific activity reducing agents such as Bun3Sn-T and tritiated Schwartz reagent; direct synthesis of labelled peptides using non-radioactive precursor peptides; preparation of DNA oligomers with labelled nucleosides; a detailed study of new and/or improved stereo- and regioselective synthetic tritiation techniques; and tritium NMR studies of ligand/macromolecule binding interactions. Service and Training operations will continue at the same level as they have in the past with an anticipated 15-25 users per year. We expect all of the Service projects will involve drug development, disease control, metabolism research or some other health-related topic, and greater than 50% of the projects will be conducted under Federal support. Training operations will continue to include a three day workshop on "Tritium Labelling and Analysis", which will be offered at least once annually, and more often if dictated by demand. All Research, Service and Training efforts are greatly enhanced by the very special environment at the NTLF, which has a unique confluence of instrumental and personnel resources. This will be emphasized by continuing collaborative efforts with industrial and academic scientists, bringing their expertise to the NTLF to work with Staff members in preparing labelled compounds for use in further study by both groups.